A friend of mine had something very similar to your pen.
I would always joke that it was a 'fake' because none of my 'real' MB's ever had that happen. He was definitely crapped off about the replacement cost and never got it fixed.....
Unfortunately, several months ago he lost/had stolen his pen. I feel sorry for him now. I wish he still had it. Look after your pens and they will look after you, that's what I say
PS: There is no cheap solution, you must drink the foul medicine sometimes to get better.